Connectors

A connector is the backend that runs a relay step. Three are builtin:

You can also register custom connectors that run your own command.

Where it lives

Connectors are configured under relay in the config file. The block has four keys:

roles and circuits reference a connector by kind (builtin or named). A named reference must point at a connector registered under connectors.

Example

relay:
  default: auto
  roles:
    researcher:
      kind: builtin
      name: codex
    implementer:
      kind: builtin
      name: claude-code
  circuits:
    review:
      kind: named
      name: my-linter
  connectors:
    my-linter:
      kind: custom
      name: my-linter # must match the registry key
      command: [my-linter, --json] # argv list, no empty elements
      prompt_transport: prompt-file
      output:
        kind: output-file
      capabilities:
        filesystem: read-only
        structured_output: json

Custom connectors

A custom connector descriptor takes these fields:

These rules are enforced at parse time:

• Custom connectors must declare filesystem: read-only. Writable custom workers are not yet supported.
• The registry key and the descriptor name must match.

Because a custom connector is read-only, it cannot fill the implementer role: that role writes. Use a builtin for implementer; use custom connectors for researcher and reviewer.

The relay block parses strictly: unknown keys are rejected.

Power tier tables

The power dial never names models. Each connector carries a tier table that translates low, medium, and high into a concrete model or reasoning effort. Two of the builtins ship with defaults: claude-code maps the tiers to Anthropic's small, middle, and big model aliases; codex maps them to reasoning effort. cursor-agent and custom connectors have no table until you declare one under the top-level power_tiers key:

power_tiers:
  my-ollama:
    low: { model: { provider: custom, model: qwen3-coder } }
    medium: { model: { provider: custom, model: qwen3-coder-plus } }
    high: { model: { provider: custom, model: qwen3-max } }

A declared tier overrides only that tier of that connector; shipped defaults fill the rest. Without a table, the dial is inert for that connector.

What a custom command receives

Circuit appends two paths as the final two arguments of your command: the prompt file to read and the output file to write. The subprocess inherits Circuit's environment and working directory, plus the resolved selection:

This is the seam for local workers: wrap a local agentic CLI in a small script, point power_tiers.<name> at your local model names, and the power dial drives local model choice with no engine changes.

Related

• Selection
• Power, process, and modes